HD64F3437TF16 Datasheet, PDF (486/752 Pages) Hitachi Semiconductor – 12 V must not be applied to the S-mask model (single-power-supply specification), as this may permanently damage the device.

20.4.2 Program-Verify Mode
In program-verify mode, after data has been programmed in program mode, the data is read to
check that it has been programmed correctly.
After the programming time has elapsed, exit programming mode (clear the P bit to 0) and select
program-verify mode (set the PV bit to 1). In program-verify mode, a program-verify voltage is
applied to the memory cells at the latched address. If the flash memory is read in this state, the
data at the latched address will be read. After selecting program-verify mode, wait 4 µs or more
before reading, then compare the programmed data with the verify data. If they agree, exit
program-verify mode and program the next address. If they do not agree, select program mode
again and repeat the same program and program-verify sequence. Do not repeat the program and
program-verify sequence more than 6 times* for the same bit.
Note: * Keep the total programming time under 1 ms for each bit.
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